People, people, really, even IF Ubuntu is "killing Debian" (which is utter nonsense), than you'll just have to learn to live with it! It's the evolution of distro's that's responsible. This evolution is created by the open-nes that we all like. Some distro's die, others rise.

If Ubuntu wants to fork away from Debian, than it's their good right. Nowhere is it said in the law that "Thou shall not fork Debian". If then that fork becomes more succesful than Debian itself, than it means Debian is doing something wrong, and the fork is doing something right. Simple as that.

Except that Debian is not your typical "almost unknown, one-man distro"
Debian is the basis for more than 120 distros.
If Debian disappears it is the beginning of the end for linux.
If somebody hated linux, what would they do for a start? Weaken and eventually kill the most used distro.